Axial split-pin tumbler-type lock

ABSTRACT

An axial split-pin tumbler-type lock includes a lock cylinder and a barrel assembly within the cylinder and including rotatable and stationary parts carrying the tumbler elements. The lock includes an end closure flange having slot means and cooperating with a post on the rotatable part for limited access through the slot means to the elements carried by the rotatable part. The latter elements travel beneath the flange during turning movement of the rotatable part between angularly spaced apart locking and unlocking positions, so that a lock pick is prevented from following the elements as they turn. A tumbler element in the stationary part is located beneath the flange and will act to enter a tumbler bore in the rotatable part for engaging the part in a difficultly hidden position, to prevent further turning movement and thereby thwart a picking attempt, in the event that an initial picking operation is successful. Angularly spaced apart slots in the flange and tumbler elements in the stationary part in alignment with respective slots provide for insertion and removal of a key in the locking and unlocking positions, for turning the rotatable part from either position to the other upon insertion and for securing the part against rotation and safeguarding the lock code upon removal in each position.

ilnited States Patent Kerr [11] 3,813,906 June 4,l974

[ AXIAL SPLIT-PEN TUMBLER-TYPE LOCK 7s lnventor: William J. Kerr, Glenview, m.

[73] Assignee: Chicago Lock Co., Chicago, Ill.

[22] Filed: Apr. 25, 1973 [21] Appl. No.: 354,449

[52] US. Cl. 711/363, 70/419 [51] Int. Cl E05b 27/08 [58] Field of Search 70/363, 358, 416, 419, 70/421 [56] References Cited UNITED STATES PATENTS 1,494,765 5/1924 Barrett 70/363 2,298,698 10/1942 Hofmann 70/358 3,380,268 4/1968 Perrill 70/363 3,541,819 11/1970 Kerr 70/363 FOREIGN PATENTS OR APPLICATIONS 504,473 7/1920 France 70/363 Primary Examiner-Robert L. Wolfe Attorney, Agent, or FirmNorman H. Gerlach [57] ABSTRACT An axial split-pin tumbler-type lock includes a lock cylinder and a barrel assembly within the cylinder and including rotatable and stationary parts carrying the tumbler elements. The lock includes an end closure flange having slot means and cooperating with a post on the rotatable part for limited access through the slot means to the elements carried by the rotatable part. The latter elements travel beneath the flange during turning movement of the rotatable part between angularly spaced apart locking and unlocking positions, so that a lock pick is prevented from following the elements as they turn. A tumbler element in the stationary part is located beneath the flange and will act to enter a tumbler bore in the rotatable part engaging the part in a difficultly hidden position. to prevent further turning movement and thereby thwart a picking attempt, in the event that an initial picking operation is successful. Angularly spaced apart slots in the flange and tumbler elements in the stationary part in alignment with respective slots provide for insertion and removal ofa key in the locking and unlocking positions, for turning the rotatable part from either positionto the other upon insertion and for securing the part against rotation and safeguarding the lock code upon removal in each position.

13 Claims, 12 Drawing Figures AXIAL SPLIT-PIN TIJMBLER-TYPIE LUCK This invention relates to an axial split-pin tumblertype lock, more particularly, to a tamper-resistant lock of such type.

Heretofore, various locks of the axial split-pin tumbler type have been devised, having means designed to render them tamperor pick-resistant. Also, lock keys have been designed together with their locks to render the keys difficult to duplicate. The prior locks and keys have achieved varying degrees of success in preventing or forestalling the opening of the locks by unauthorized persons. Generally speaking, it is possible ultimately to pick any key-operated lock, and efforts to prevent unauthorized picking are based on rendering the operation difficult and time-consuming, and, also, making it difficult to design a successful pick. In some instances, duplication of keys has been restricted by key designs that are not readily reproduced with conventional equipment, such as used by locksmiths, but, instead, require specialized equipment.

An object of the present invention is to provide a new and improved tamperor pick-resistant lock of the axial split-pin tumblertype and, in particular, a lock which resists picking by the means and methods previously employed to open locks of this type.

Another object is to provide a lock of the axial splitpin tumbler-type in which access to the lock tumblers is limited so as to make it difficult to perform a picking operation and difficult also to turn a picking tool or instrument with the tumblers for unlocking purposes in the event that an initial picking step or operation is successful.

An additional object is to provide a lock of the foregoing character in which at least one tumbler is concealed from the outside and is at least difiicultly accessible when a rotatable barrel assembly part reaches an intermediate position between operational positions thereof, especially a position intermediate locking and unlocking positions thereof, so that should the lock be picked initially and the barrel part rotated part way towards its unlocking position, the tumbler will operate to re-engage the rotatable part with a stationary part in the intermediate position and prevent further movement of the rotatable part, thus foiling the picking attempt.

A further object is to provide an axial split-pin tumbler-type lock which, in a preferred embodiment, is constructed for insertion and removal of its key in each of two angular positions of a rotatable barrel assembly part, which may correspond to locking and unlocking conditions of the lock, and which yet provides but limited access to the lock tumblers as described above in both conditions of the lock while the tumblers are engaged to secure the lock mechanism when the key is re moved.

A still further object is to provide a lock accomplishing the foregoing objects and which also is operated by a key that is difficult to duplicate with conventional equipment, such as employed by locksmiths, and, in particular, cannot be made from a blank in the common manner or turned on a lathe as in the case of a circular shank key. An accompanying object is to provide such a lock that enables numerous key changes:

A particular object is to provide a key for a lock of the foregoing character, which key is constructed with tangs serving the multiple purposes of carrying the key 2 bittings, holding the bittings in engagement with the lock tumblers to disengage the same for operating the lock, and retaining the key in the lock during operation thereof.

Another object is to provide a lock accomplishing the foregoing objects and which also is relatively simple and economical in construction and use.

These and other objects, advantages and functions of the invention will be apparent on reference to the specification and to the attached drawings illustrating a preferred embodiment of the invention, wherein like parts are identified by like reference symbols in each of the views, and wherein:

FIG. I is a perspective view of a key which cooperates with the lock of FIG. 4, in accordance with the invention;

FIG. 2 is a side elevational view of the key;

FIG. 3 is an end elevational view of the key;

FIG. 4 is a perspective view of a lock according to the invention;

FIG. 5 is an elevational view of the lock and key, the lock being illustrated in exploded view with but part of certain springs and tumbler element pins shown and with a cylinder part partly broken away and in section;

FIG. 6 is an enlarged longitudinal sectional and partly elevational and broken view of the lock, taken substantially on lines 6-6 of FIG. 10;

FIG. 7 is a view similar to FIG. 6, but showing the lock with the key inserted therein and taken substantially on lines '77 of FIG. 10;

FIG. 8 is a front end elevational view of the lock,

taken substantially on line 88 of FIG. 6 and on a reduced scale;

FIG. 9 is a cross-sectional view of the lock, taken substantially on line 9-9 of FIG. 6 and on a reduced scale;

FIG. 10 is a cross-sectional view of the lock, taken substantially on line ltlll0 of FIG. 7 and on a reduced scale; and

FIGS. It and I2 are, respectively, schematic views similar to FIG. 8 but showing the lock cylinder in phantom lines, illustrating the disposition of the lock tumblers and the bores in which the tumbler elements are mounted, in the locking and unlocking conditions of the lock.

The invention relates to an axial split-pin tumblertype lock having a lock cylinder and a barrel assembly secured within the cylinder, the barrel assembly including respective rotatable and stationary parts adjoining each other at an interfacial plane. Longitudinal bores are provided in the rotatable and stationary parts, with the bores in respective parts being movable into and out of alignment upon rotation of the rotatable part. Tumblers having elements carried by the bores are reciprocatable longitudinally in aligned bores, from a position wherein the interfacial plane is bridged by a tumbler element to secure the rotatable and stationary parts against relative rotation, to a position wherein the interfacial plane coincides with a tumbler joint to free the parts for relative rotation. Spring means yieldingly urge the tumblers into the position securing the parts.

In the invention, an end of the cylinder is provided with an inwardly extending annular flange which defines a central circular opening into the cylinder and slot means extending radially outwardly from the opening. The bores in the barrel assembly parts are disposed radially outwardly of the flange opening and portions of the aligned bores are aligned with the slot means to provide access to the tumblers through the slot means. A circular post is connected to the rotatable part for conjoint rotation, and it has an outside diameter approximating the diameter of the flange opening. The post extends into the flange opening to restrict access to the interior to the cylinder through the opening. A transverse lteyway is provided in the post and is registrable with the slot means, whereby a key may be inserted into the keyway and slot means for moving the tumblers into their positions freeing the barrel assembly parts and for turning the rotatable part.

An additional longitudinal bore is provided in the stationary barrel assembly part and is disposed radially outwardly of the flange opening and out of alignment with the slot means, the additional bore being aligned with one of the bores in the rotatable part in an intermediate position of the rotatable part between operational positions thereof. An additional tumbler element is carried in the additional bore and forms a complete tumbler with a tumbler element carried in the aligned bore in the rotatable part, such complete tumbler alternately securing and freeing for relative rotation the rotatable and stationary parts, as in the case of the firstmentioned tumblers. Additional spring means yieldingly urge the complete tumbler into its position securing the parts. A key may be inserted and the rotatable part turned thereby, beyond the aforesaid intermediate position, to complete the turning movement of the rotatable part. in the absence of the key, the rotatable part is secured by the complete tumbler against further turning movement upon reaching the intermediate position. The intended ultimate position cannot be reached, so that a picking attempt is foiled.

in a preferred embodiment, useful independently of the foregoing structure providing an additional tumbler element, the flange on the end of the cylinder defines a central circular opening having at least two slots extending radially outwardly from the opening in angularly spaced relation and registrable alternately with the keyway. The aforementioned bores aligned with the slot means are in alignment with a first one of the slots, and further longitudinal bores are provided in the stationary part and aligned with a second one of the slots. Such further bores are aligned with certain of the bores in the rotatable part, and portions of the resulting aligned bores are aligned with the second slot upon effective completion of the turning movement of the rotatable part. Further tumbler elements are carried in the further bores and form complete tumblers with tumbler elements carried in the aligned bores in the rotatable part. Such complete tumblers are accessible through the second slot and are reciprocatable between positions respectively securing and freeing for relative rotation the barrel assembly parts, as in the case of the first-mentioned tumblers. Further spring means yieldingly urge the latter complete tumblers into their positions securing the parts. A key may be inserted into and removed from the keyway and one of the slots in each of two angular positions of the rotatable part, for turning the same from either position to the other upon insertion and for securing the same against rotation and safeguarding the lock code upon removal in each position. In each case, it is further preferred that the tumblers abut on the flange when in their positions securing the rotatable and stationary parts.

The invention also provides in combination with the lock, a key having a shank received in the keyway, and a tang on the shank and insertable through a slot and internally of the cylinder beyond the flange, the tang having bitting means thereon and engaging the tumblers for moving them into their positions freeing the parts for relative rotation, and the tang turning behind the flange and being retained in the lock by the flange as the key is turned, preferably while also retaining the tang in operative engagement with the tumblers. Additional features of the invention are described hereinafter.

Referring to the drawings, particularly FIGS. 1-5, an axial split-pin tumbler-type lock 20 is employed with a key 22 according to a preferred embodiment of the invention. The illustrative specific embodiment of the lock is identified as a switch lock, but the invention is not limited thereto, and includes other specific lock types, such as the cam lock" illustrated in my [1.5. Pat. No. 3,541,819. The key 22 is, however, ofa different type, being referred to as a flat" key, as distinguished from the round or "circular" type of key disclosed in the foregoing patent, the description referring particularly to the shank portions of the respective keys. The key of the present invention, nevertheless, is not limited to a truly flat shank structure, but, in fact, the shank may assume other non-circular configurations, such as cross-shaped.

Referring to FIGS. 4-7, the lock 20 includes a twopart lock cylinder, constructed of a tubular outer cylinder part 24 and a tubular inner cylinder part 26. The inner part 26 is received closely within the outer part 241 and fixed thereto, as described hereinafter. A twopart barrel assembly is received closely within the lock cylinder, and is made up of a plug or spindle member 28 rotatable in a stationary sleeve member 30. A stop disc 3t is received on the plug member 28 and cooperates with the inner cylinder part'26 to limit the rotation of the plug member 28, as described hereinafter. The lock is operated by turning the plug member 28.

Tumbler elements are carried by the respective plug and sleeve members, including driver pins 32 carried by the plug member 28, and follower or locking pins 34 having stems 36 carried by the sleeve member 30. Coil compression tumbler springs 38 are carried by the sleeve member 30 and received around the follower pin stems 36., A coil compression resistance spring 40 also is carried by the sleeve member 30, and a resistance ball 42 is carried by the sleeve member and engaged by the resistance spring 4%. The lock tumblers consisting of the driver pins 32 and the follower pins 34, under the force of the tumbler springs 38, function to secure the plug member 28 and the sleeve member 30 against relative rotation, and are movable by the key 22 to free the plug and sleeve members for relative rotation, while the ball 42 provides an added resistance to plug turning, as described hereinafter.

The following structural elements are peculiar to a switch lock and are merely illustrative of one of the applications of the basic lock structure of the invention: A coupling as is received within the outer cylinder part 241 and engages the plug member 28 for rotation therewith. The coupling as also engages a conductor carrier $3 for conjoint rotation, and a coil compression biasing spring 5t) is interposed therebetween. A barbell conductor 52 is received in the carrier 48. A terminal mounting 54 receives the carrier 48 and the conductor 52, and itself is received in the outer cylinder part 24 and provides a rear end closure thereon.

The outer cylinder part 24 is constructed for mounting the lock 26 in an opening in a wall, door, or other suitable member of a housing, cabinet or other structure (not shown) which in the case of the illustrative embodiment may house an electrical control system. in other embodiments, wherein the switch structure is replaced by a locking arm or plate in a cam lock, as re ferred to hereinafter, the lock may be mounted on a machine or device for dispensing merchandise or changing money, for example, and the lock controls ac cess to the interior thereof.

The outer cylinder part 24 includes a threaded substantially cylindrical body 55 having a longitudinally extending flat surface 56 thereon and a hole 58 therethrough. An enlarged frusto-conical head 60 is integral with the body 55 at its front or normally outer end, and switch-mounting extensions 62 extend longitudinally from the rear or inner end of the body 55. The interior of the outer cylinder part 24 is substantially cylindrical, except for an integral inwardly projecting circular retaining flange 64. The body 55 is inserted through an opening in a wall, door, or other member, and it may be clamped thereto in the conventional manner of mounting this type of lock, i.e., by means ofa threaded nut (not shown) engaging the body 55. Thus, a wall panel may be clamped between the head 68 and such a nut, leaving the head protruding and accessible from the outside of the structure.

The inner cylinder part 26 includes a cylindrical tubular body 66 having a hole 68 registering with the hole 58 in the body 55 of the outer part, and a second, smaller hole 70 adjacent thereto. An arcuate longitudinal extension 72 is provided on the rear or normally inner end of the body 66, and it forms stop shoulders 74 on opposite sides thereof.

As seen in FlGS. 4i and 6-8, an annular closure flange 76 is integral with the front or normally outer end of the inner cylinder part 26, and the flange extends radially inwardly from the body66. The flange defines a central circular opening 78 and slot means extending radially outwardly from the opening. The slot means provide two pairs of diametrically opposed generally rectangular slots 86,82 and 84,86, as numbered for each pair.,The several slots are spaced at preferred angles of 90 around the central opening 78. Four arcuate flange portions 88 (FIG. 8) remain between the several slots, such portions extending to the margin of the central opening 78. The interior of the inner lock cylinder part 26 is cylindrical, except for an inwardly extending circular ring 90 (FIGS. 6 and 7) integral with the body 66 and adjoining the closure flange 76 at the inner surface 94 of the flange. The ring 90 forms an inner, rearwardly facing shoulder 92 on the body 66.

As seen in FIGS. 6 and 7, the inner cylinder part 26 receives the barrel assembly composed of the plug member 28 and the sleeve member 36, together with the tumbler pins 32 and 34, the tumbler springs 38, the resistance spring 40, and the resistance ball 62. The sleeve member 30 is fixed within the cylinder part 26. The plug member 28 is rotatably mounted in the sleeve member 30.

The plug member 28 includes a cylindrical head 98 having two pairs of longitudinal bores Rl, R2 and R3,

R4 (FlG. 9) having equal diameters and extending through the head at equal distances or radii from the axis of the plug member. The bores in each pair are spaced apart at a preferred angle of 30, and individual bores of the respective pairs are diametrically opposed to each other. A round detent 100 (FlG. 6) is formed in the inner or under surface 162 of the head 98, and is spaced at a preferred angle of 30 from a bore R2.

A cylindrical post 164 is integral with the head 98 and extends coaxially from the outer surface T05 thereof (FIGS. 5-8). The diameter of the post approximates the diameter of the closure flange opening 78. A keyway H86 in the form of an asymmetrical groove extends longitudinally in the post throughout its length, to its junction with the head 98. The keyway is in the shape of a shallow V, but it may take other preferably asymmetrical forms. A cylindrical lock shaft 108 is integral with the head 98 on the opposite side from the post 184, and extends from the inner surface T62 of the head coaxially with the head. A pair of flats 110 is provided on opposite sides of the lock shaft at its free end. While the plug member 28 in the illustrative embodiment is a one-piece construction of the head 98, the post T64 and the lock shaft 168, the post 104 and/or the lock shaft 188 may be made separately from the head 98, from the same or different materials, and suitably assembled therewith.

The plug member 28 is received within the inner cylinder part 26 with the post T84 extending into the closure flange opening 78, to restrict access to the interior of the cylinder through the opening. The keyway T06 registers alternately with the pairs of slots 88,82 and 84,86. The key 22 may be inserted into the keyway T06 and either pair of slots. As seen in FIGS. 6 and 7, the outer surface 185 of the plug member head 98 abuts on the shoulder 92 formed by the ring 90 and the body 66, thus retaining the plug member 28 in the inner cylinder part 26. The head 98 fits closely within the body 66 for rotation therein. The post 104 and the lock shaft T08 rotate conjointly with the head 98.

The sleeve member 36 is a cylindrical tubular member having a socket llll2 (FlGS. 5 and 16) extending from its outer surface into the wall thereof and an adjacent smaller hole TM extending through the wall. The lock shaft 168 is received closely within the sleeve member 30 for rotation of the shaft therein. The outer end surface T69 of the sleeve member 30 adjoins the inner surface 102 of the plug member head 98 at a transverse interfacial plane H6, as identified in broken line in FIGS. 6 and 7.

The barrel assembly consisting of the plug member 28 and the sleeve member 36 is assembled together with the driver pins 32, the follower pins 34, the tumbler springs 38, the resistance spring 49, the resistance ball 42, and the inner lock cylinder part 26 in an operating sub-assembly. The parts are secured together by means of a drive-fit pin Hi8 (FlG. 5) inserted into the small hole 78 of the cylinder part 26 and the small hole lid of the sleeve member 36, so that the parts are assembled as illustrated in FIGS. 6 and 7. The subassembly is further assembled with the stop disc 31 and the coupling 46, as subsequently described in greater detail, and the resulting assembly is inserted through the front end of the outer cylinder part 24 and secured therein by a drive-fit knurl pin i (FIGS. Sand R0). The ltnurl pin 126 extends through the hole 58 in the outer cylinder part 24 and the registering hole 68 in the body 66 of the inner cylinder part 28, and into the socket 112 in the sleeve member 30, to secure the cylinder parts and the sleeve member together.

As seen in FIG. l0, longitudinal bores or sockets Si through S9 are provided in the wall of the sleeve member 3h). The bores Sit-S9 have equal diameters and are disposed at equal distances or radii from the axis of the sleeve member 36 which coincides with the axis of the plug members 28., Such disposition and diameters of the bores Sl-S9 are the same as for the plug member bores Rli-Rd, to provide for alignment of respective bores, as subsequently described. The sleeve member bores are arranged in two groups, and the bores in each group are centered at 30 angles to each other. The bores in one group are identified, in clockwise order, as Sll through S5. The bores in the remaining group commence at an angular spacing of 60 from the first group, and are identified, in clockwise order, as S6 through S9. The bore S9 is at an angular spacing of 90 from the bore St, to accommodate the socket M2 in the sleeve wall.

Referring to H08. 6 and ill, the bores Sl-S9 in the sleeve member 30 are closed at their inner ends, and each receives a coil compression spring. A tumbler spring 38 is received in each of the bores 811, S2, and S4! through 39, and the larger resistance spring 40 is received in the bore S3 constituting the central bore in one set of bores. A follower pin 34 is received in each of the bores S1, S2, and S4 through S9, with the stem S6 thereof received within a spring 38. The follower pins 34 have a diameter slightly less than the diameter of their sleeve member bores and also of the plug member bores RlR4l, for a loose sliding fit allowing for longitudinal reciprocation in the bores. The follower pins preferably are of at least two different lengths, for security purposes as explained hereinafter. The follower pins 34 are considered as being carried by the sleeve member Bil, although, as will appear, these elements at times extend into the bores Rll-R4 in the plug member 28.

Four driver pins 32, each of which preferably has a different length, are carried by respective bores RllRd in the head 98 of the plug member 28. The driver pins 32, like the follower pins 34,'have diameters slightly less than the diameters of the bores Ril-Rl, so that the driver pins are longitudinally reciprocatable in the bores.

A tumbler is formed by a driver pin 32 and a follower pin 34 as tumbler elements, when they are in aligned plug member and sleeve member bores, as illustrated in H68. 6 and '7, wherein the bores R4 and S7 are shown in alignment. At this time, the follower pin 34 abuts on the driver pin 32, and the complete tumbler is subjected to the force of the tumbler spring 38, which yieldingly or resiliently urges the tumbler outwardly or towards the front of the lock 26. The tumbler is reciprocatable longitudinally in the aligned bores-R4 and S7, from a position wherein the interfacial plane M16 is bridged by the follower pin 34, as illustrated in F116. 6, to a position wherein the interfacial plane llllti coincides with the tumbler joint at the abutting surfaces of the follower pin 34 and the driver pin 32, as illustrated in F K]. '7. The first position is attained when the tumbler spring 38 urges the tumbler pins 32 and 34 outwardly until the outer, driver pin 32 abuts on the inner surface 94 of the closure flange 76. This position normally obtains when the key 22 is removed from the lock, and as a result, the plug member 28 and the sleeve member 34 are interengaged by the follower pins 34, and the plug member is prevented from turning. The second position normally obtains when the key 22 is inserted into the lock, to engage and depress the tumblers, so that the joints between the driver pins 32 and the follower pins 34 coincide with the interfacial plane H6, thereby disengaging the rotatable plug member 28 from the stationary sleeve member 30 and freeing the plug member for relative rotation.

inasmuch as there is a greater number of follower pins 34 and corresponding bores 51, S2 and S4S9 than the number of driver pins 3?; and corresponding bores Rib-R4, there are present always a number of follower pins, such as the pin 34a illustrated in H6. 7, that are not paired with a driver pin to form a complete tumbler. This condition also obtains for all follower pins 3d when the lock is being operated and the plug member 2355 is in a rotational position between positions of alignment of the respective plug and sleeve member bores. In such condition, the unpaired follower pins, such as the pin 34a, abut on the inner surface E02 of the plug member head 98. Each unpaired follower pin continues to abut on the head surface 392 until its bore S5 or the like becomes aligned with one of the bores Rl-R4 in the head 98, upon rotation of the plug member 28. At such time, the previously unpaired follower pin forms a complete tumbler with one of the driver pins 32, and operates in the manner described above.

As seen in FlG. 6, the resistance ball 42 is received in the bore S3, on the outer end of the resistance spring an. in this initial or starting condition of the lock, the resistance ball 42 projects from the bore S3 to engage the detent Elli) of the plug member head S98, thereby providing a so-called false resistance to picking. As the lock is being operated, the ball d2 successively contacts the inner ends of the driver pins 32 in the bores R2 and Rll. The ball 42 contacts the inner surface 102 of the head 9%? in the final condition of the lock, illustrated in H6. 12.

Referring particularly to FlGS. 8-l2, it will be seen that the bores RhiRd in the rotatable plug member 28 and the bores Sl-S9 in the stationary sleeve member 30 are disposed radially outwardly of the opening 78 in the closure flange 76. Portions of certain of the bores in the sleeve member fit), which may be termed primary or operating bores, are in alignment with the slots 80,8234, and 86. Thus, approximately one quadrant of each of one pair of bores Sit and S2 is in alignment with slot 80 at one of the outer corners thereof. Likewise, portions of the pair of bores S4 and are in alignment with the slot S 1; portions of the pair of slots S6 and S7 are in alignment with the slot 82; and a portion of the bore S9 is in alignment with the slot 86. The bores S3 and SS, which may be termed secondary or security bores, are out of alignment with the slots and are behind the flange portions 88.

Portions of the plug member bores R1414 are in alignment with the slots when the plug member 28 is in a position wherein the bores Rl-R4 are aligned with certain bores in the sleeve member 30. Such alignment obtains when the lock is in its initial condition as illustrated in FlGS. fl and ill, and when in its final condition, as illustrated in Flt}. 12. Thus, the plug member bores Hi and R2 are in alignment with respective sleeve member bores Sll and S2 and with one slot 80 in the initial condition of the lock. The plug member bores Rl and R2 are in alignment with the sleeve member bores S4 and S5 and with the next succeeding slot 84 in the final condition of the lock. The plug member bores R3 and R4 are in alignment with sleeve member bores S6 and S7 and with one slot 82 in the initial condition. The plug member bore R3 is in alignment with the sleeve member bore S9 and with the next succeed ing slot 86 in the final condition of the lock. in the latter condition, there is no sleeve member bore corresponding to and in alignment with the plug member bore Rd, although the latter bore is in alignment with the slot 86. Portions of the driver pins .32 of the turnblers thus are aligned with and accessible through one pair of opposed slots 88,82 in the initial condition of the lock, and the pin portions are aligned with and accessible through the remaining pair of slots 84,86 in the final condition of the lock.

The key 22 is insertable into and removable from the lock 26) in either of its initial and final conditions. in ei ther condition, the key is inserted into the keyway 1% and a pair of slots registering therewith, the slots 88,82 or the slots 84,86, as the case may be. Referring to FlGS. 1-3, the key 22 includes a wing-type manipulating handle R22 and an integral shallow V-shaped shank 124. Tangs E26 and 128 are integral with the shank 124 and extend laterally outwardly from opposite sides of the shank. The tangs are cut away to form four bittings, ll3ll-l33 on them, with two bittings i138 and 131 being formed on opposite sides of one tang 1126 and two bittings 132 and 1133 being formed on opposite sides of the other tang 128. The tangs 126 and 128 have a depth substantially equal to the depth of the ring 90 on the inside of the inner cylinder part 26 (see WC. 7), and the bittings Mil-I33 have different depths corresponding to the respective lengths of the driver pins 32. The key shank 124 is inserted into the keyway 106, and the tangs 126 and 128 are inserted into the respective slots 88 and 82, or 84 and 8d. The bittings 3130-133 engage respective driver pins 32 of the tumblers for moving the tumblers into the position illustrated in H0. 7, freeing the plug member 28 for rotation and for then turning the plug member and connected lock shaft 1188.

Referring to FIGS. 5 and 6, the stop disc 31 is provided with an elongated opening 136 for receiving the lock shaft 308 and particularly the end portion thereof having the flat surfaces 110, for conjoint rotation of the parts. The disc is provided with a pair of projecting shoulders 138 which are adapted alternately to engage one or the other of the stop shoulders '74 on the extension 72 of the inner cylinder part 26, in alternate positions of the disc at an angular spacing of 90 between positions. in this manner, rotation of the plug member 28 in the illustrative embodiment is limited to 90, in a clockwise direction from the position illustrated in FIGS. 8 and 11 to the position illustrated in FlG. l2, and counterclockwise from the latter position to the former position.

Referring to FIGS. 5 and 6, the illustrative coupling 46 is constructed of insulative plastic. it is a circularly shaped member having an annular rim Mil which may bear or seat on the retaining flange 64 on the inner surface of the outer cylinder part 24. An elongated recess M2 is formed in one end of the coupling, and it receives the inner end of the lock shaft M8 for rotation therewith. A circular recess M4 is provided in the opposite end of the coupling, and it receives one end of the biasing spring 50. The coupling also has a pair of kit lid

spaced opposed legs 146, which receive the conductor carrier $8 for rotation therewith.

The carrier 48 is provided with a boss M8 for centering the other end of the biasing spring 50 thereon, and with a cavity l5 on the opposite side thereof receiving the barbell conductor 52. The lock is completed by the terminal mounting 54, which includes a pair of spaced opposed arcuate side walls 151 receiving a portion of the carrier 48 and the conductor 52 for rotation therebetween. A pair of terminals 152 is secured in the mounting 5 1 and terminate in internal contacts 54. The conductor 52 is adapted upon rotation alternately to bridge the contacts H54 to complete a circuit, and to break contact therewith to open the circuit. The terminal mounting 54 is received and clamped by the extensions 62 of the outer cylinder part 24, while the side Walls llSl close the spaces between the extensions.

in use, the lock 24) in the initial condition illustrated in FlGS. '8 and 8 is in what is referred to as its locking condition or attitude, and particularly, in the locking positions of the plug member 28 and the lock shaft 108. However, it will be apparent that, alternatively, condition may constitute the unlocking condition, if desired. In the initial condition, the four bores in the cylinder head 98 are aligned with four bores in the sleeve member 30, the aligned bores being identified as R1 and 51, R2 and S2, R3 and S6, and R4 and S7. The tumbler elements represented by the driver pins 32 and the follower pins 3@ in the respective bores form complete tumblers, which are urged by the tumbler springs 38 into abutting engagement with the inner surface 94 of the closure flange 76. The four follower pins 34 bridge the interfacial plane lid, to secure the rotatable plug member 28 and the stationary sleeve member 3% against relative rotation. The lock shaft 108 and the coupling as, the conductor carrier 48 and the conductor 52 connected for rotation with the lock shaft likewise are secured against rotation. in the illustrative switch, the contacts R54 are open. Alternatively, the structure may be altered so that the contacts are bridged by the conductor 52 at this time, according to the intended function of the electrical circuit.

in the foregoing condition of the lock, the resistance ball 42 is urged into engagement with the detent 100 in the plug member head Q8, by the resistance spring 40 carried by the sleeve member bore S3. The follower pins 34 carried by the sleeve member bores S4, S5, S8, and S9, are in the condition illustrated by the pin 34a in FlG. '7, wherein the pins are urged by the tumbler springs 38 into abutting engagement with the inner surface W2 of the plug member head 98, such surface coinciding with the interfacial plane U6. The resistance ball 42 affords a certain resistance to plug member turning, but may be cammed into the bore S3 by the plug member head 98 when the head is turned. The follower pins in the condition of the pin 34a afford no substantial resistance to turning of the plug member 28.

As illustrated in H6. 8, the driver pin elements 32 of the tumblers are accessible through the slots and 82 in the closure flange 7s. As seen in FIG. ll, the sleeve member bores S3 and S8 carrying, respectively, the re sistance ball 42 and a follower pin 34, are out of alignment with the slots and, instead, are aligned with and covered by arcuate flange portions 88. The remaining sleeve member bores S4, S5, and S9, are aligned in part with the slots 84 and 86, while being covered by imperforate portions of the plug member head 98.

llll

When the key 22 is inserted into the keyway Ellis and the slots h ll and 82 of the lock 20 in its locking condition, the bittings 1230-133 engage the outer ends of the driver pin elements 32 of the tumblers and depress the same, as illustrated in FlG. 7. When the key shank R24 is bottomed in the keyway we, the driver pins 3.2 are depressed to the extent that their inner ends or faces and the tumblerjoints formed thereat coincide with the interfacial plane ll 16, to free the rotatable plug member 28 and stationary sleeve member 30 for relative rotation. The key then may be turned in the clockwise direction, as seen in FIG. b, thus turning the plug member 28, the lock shaft W8 thereof, and the coupling 46 and switch parts connected to the coupling.

As described above, the key tangs i126 and H28 are sized to a depth equal to the depth of the ring 9@ in the inner cylinder part. 26, so that the outer edges of the tangs substantially abut on the inner surface 4 of the closure flange 76, as illustrated in FIG. 7. Several functions are achieved by this construction: The tangs pass under the closure flange m, as the key is turned, so that the driver pins 32 may be maintained with their inner ends at the interfacial plane llllb as the key is turned. The key is maintained in the lock by the closure flange 76 during turning, and, advantageously, the key is maintained at the correct inserted position to properly position the driver pins 32 for rotation without need for further manipulation by the person holding the key. There is then no danger that tumbler pins will be broken due to in and out movement of the key with consequent longitudinal pin movement during turning.

As the key is turned to turn the plug member 28 from the initial position illustrated by its pos lltM in FIG. ill to the post position illustrated in FlG. l2, the driver pins 32 carried by and filling the plug member bores Rl-R4 pass over the intervening resistance ball 42 and follower pins 34 without interference. When the position of FIG. 12 is reached, alignment of the bores R11 and S4, R2 and S5, and R3 and S9 is attained. There being no corresponding bore in the sleeve member 3'13, the remaining bore R4 reaches a blank position with respect to the sleeve member. in this condition of the lock, complete tumblers are formed by the driver pins 32 and the follower pins 34 in the respective aligned bores, and portions of the aligned driver pins are aligned with the slots 84 and $6. The remaining sleeve member bores 51-83 and S6438 are out of alignment with the plug member bores, so that the follower pins 34 and the resistance ball 42 therein abut upon the flat inner surface m2 of the plug member 98, as illustrated for the follower pin 3 3a in FlG. 7'.

At this time, the key 22 may be removed from the lock 20, through the slots 84 and 86, so that the tumbler elements 32 and 341 in the aligned bores once more secure the rotatable plug member 28 and the stationary sleeve member 30 against relative rotation, with the tumblers in the position illustrated for one tumbler in FIG. 6. The parts are secured in the unlocking condition of the lock 2ft in the same manner as they are secured in the locking condition, although providing but three complete tumblers rather than four as in the locking condition. The conductor 52 is in a position rotated 90 from its starting position. to bridge the contacts 1154 and close the circuit made with the terminals 152. The lock may be restored to its initial locking condition and the circuit broken by inserting the key 22 in the keyway I106 and the registering slots 84% and $6, and turning the key in the counterclockwise direction, to reverse the operation of the lock. Upon reaching the initial condition illustrated in FlG. llll, the key is removed and the lock parts again are secured against relative rotation.

The security of the lock 2b is safeguarded by the invention in a number of ways, which greatly reduce the likelihood that the lock will be operated or picked by unauthorized persons. There is but limited access to the tumblers, at the corners of narrow slots, which restricts probing and manipulation of the tumblers. Should it be possible to successfully position all of the tumblers with a picking tool and commence turning the plug member 28, the driver pins 32 turning therewith cannot be followed beneath the overlying arcuate portions 88 of the closure flange '76 with the usual type of picking tool, and especially with the circular type requiring a circular groove or slot for rotation thereof. Access to the driver pins from the flange opening 78 is substantially prevented by the presence of the post ltld in the flange opening, the post filling the opening except for the limited access provided by the keyway we. Consequently, in the absence of a key, the plug member 28 will again become secured to the sleeve member 30 and pre vented from further turning at 30 and 60 of rotation, as the plug member bores Rll-R4 carrying the driver pins 32 become aligned with successive sleeve member bores carrying follower pins 341.

It is an important preferred feature of the invention that one sleeve member bore, identified as S8, is out of alignment with any of the closure flange slots 80,82,84, and S6, and is, instead, aligned with and covered by an arcuate flange portion 88. Referring to FIG. ll, it will be seen that when the plug member 28 is turned 30 in a clockwise direction, the plug member bore R4 and its driver pin 32 reach alignment with the sleeve member bore Sill and its follower pin 3 and a complete tumbler is formed beneath the flange portion 88. Should the plug member 28 reach this intermediate position as the result of a successful initial picking operation, the tumbler then formed will once more secure the plug member against rotation when the spring member 38 causes the follower pin 34 to bridge the interface 116, as illustrated in H6. 6. At this point, the lock is, effectively, jammed, and it cannot be unlocked. A person attempting to pick the lock will find access to the hidden tumbler very difficult to obtain, and, moreover, he is unlikely to know where the problem lies.

A cooperating feature of the invention is the structure whereby the tumblers, particularly the driver pin elements 32 thereof, abut upon the inner surface 94 of the closure flange '76, as illustrated in FIG. 6. This arrangement leaves no room for insertion of a tool between the tumbler and the flange, rendering it difficult to operate a tool, especially on a tumbler completely covered by a flange portion 88. Previously, in other lock structures, the presence of free space above the tumblers tended to facilitate picking.

The provision of the detent mil in the plug member head 9%, and the resistance ball 42 engaging the detent further increases the pick resistance. Thus, lock picking is based upon manipulation of tumblers until resistance to turning of the plug member 28 is overcome. The resistance ball 42 adds a false".resistance to turning, which is not related to the disposition of a tumbler.

Another important preferred feature of the invention is the provision for insertion and removal of the key 22 in both of the locking and unlocking conditions of the lock 2b, with the lock parts secured against rotation and the lock code safeguarded when the key is removed in each condition of the lock. Thus, for example, the illustrative switch lock may be installed in an alarm system wherein the lock is in its locking and unlocking conditions alternately for extended periods of time while left unattended. Consequently, the key must be removed after each operation of the lock, and when the key is removed, it should not be possible to return the rotatable part to its other position without a key, or to determine the lock code. The structure of the invention accomplishes these objectives, with the lock operating and being protected in the same way in each con dition.

A further feature of the invention resides in the structure of the key 22, which is not readily duplicated. Thus, either special tooling or considerable effort is required to make a key having a flat-type shank 124 and tangs 12d and T28 extending laterally therefrom, with bittings ran-r33 extending longitudinally in the direction of the axis of the key. The key cannot be duplicated by a locksmith in the'usual manner employing a blank. It cannot be turned on a lathe as in the case of a round or circular shank key.

The provision of an asymmetrical keyway ll llti in the post M94 and complementary shank T24 on the key 22 serves to orient the key in the lock. A number of key changes may be provided for the same basic lock by changing the shape or outline of the keyway 1% and its disposition with respect to the slots $032,841 and as, with corresponding changes in the key shank 124 and tangs 126 and 123. Key changes are also provided for by changing the kengths and/or relative disposition of the driver pins 32, with corresponding changes in the bittings HEW-J33.

it is preferred that the driver pins 32 be employed in four different lengths, although a lesser number might be employed, to maximize the difficulty in picking the lock. if desired, additional tumblers may be supplied, by increasing the number of bores in the plug member. The additional tumblers may be accessible through the slots 8 and/or 86 in the locked condition of P16. 8, and in this case, a generally cross-shaped key shank having additional tangs and bittings is employed. The follower pins 34 are employed in a plurality of lengths, so as to preventdisengagernent of the plug member 28 from the sleeve member 30 by the expediency of first bottoming all tumblers in the sleeve member bores, and then allowing them to move outwardly together under the force of the tumbler springs 38.. With follower pins 34 of but one length, all of "the follower pins will reach the interfacial plane 116 at the same time, to free the barrel assembly parts for relative rotation. Different length follower pins 34 also afford different picking resistance.

While the illustrative structure is employed for greater security, it will be apparent that the number of tumblers and corresponding slots in the closure flange 76 may be reduced while still providing the advantages of the invention. For example, and referring to FIGS. 8-12, the plug member bores may be reduced to those numbered Rll and R2, the sleeve member bores may be reduced to those numbered Sl-SS, and the slots may be reduced to those numbered 8d and S4. in this case, preferably, a follower pin 34 and tumbler spring 38 are mounted in the bore S3, in place of the resistance spring db and ball 42, in order to provide the security function described above in connection with the bore SS, The key then has but one tang 12s and two bittings H369 and K141.

The basic lock structure may be employed in other applications, such as in cam locks of the type disclosed in my above-identified patent. in a cam lock, an elongated locking arm or plate is secured to the outer end of the lock shaft MP8, which may be extended and also threaded for that purpose. The coupling as, the biasing spring 50 and the switch members 48, 52 and 54 are not employed.

When the cam lock construction is employed, and also in other types of locks, it is preferable frequently to provide for removal of the key in but one position, i.e., in the locking condition of the lock, providing what is referred to as a one-way key pull." This assures that when the key is removed, the structure in which the lock is mounted is locked. To achieve this objective, the slots 84 and 8d may be eliminated, and no longer is there any need for the sleeve member bores S4, S5, and S9, and their associated pins 34 and springs 38, which may be eliminated. Additionally, if desired, the slot S2 and the sleeve member bores 86-88 and their associated pins 34; and springs 35 may be eliminated, substituting a follower pin 3d and tumbler spring 38 for the resistance dill and ball 42 in sleeve member bore S3 for security purposes, as described above for the illustrated construction with reference to the sleeve member bore SS. in the latter embodiment, again, a key having but one tang and two bittings thereon is employed. However, it is also preferred in the one-way key pull structure, that four tumblers be employed for greater security.

The use of a key such as the illustrative key 22, having two opposed tangs T26 and 1128 entering opposed slots Silt and 82, or 84 and S6, and then traveling under opposed closure flange portions SS, is preferred as providing a balanced application of force in the application of the key. With a single tang, the key is more inclined to tilt as it is turned, which may cause the ends of the tumbler pins 32 and 3 .1 to move across the interfacial plane lie when not intended, thereby causing damage.

While the illustrative lock 20 is limited to rotation of the plug member 2% between operating positions at an angle of 90 to each other, the extent of the rotation during operation may be varied with suitable adjustments. For example, the range of operation may be extended to or to 360, which necessitates alteration of the stop means represented by the stop disc Bil and the cylinder extension 72, and in the latter case may entail eliminating the stop means, i.e., where turning beyond 360 is acceptable. it will be apparent that in modifications of the foregoing character, it may be advantageous or necessary to alter the spacing and/or the number of the tumbler bores and tumbler elements. For example, additional sleeve member bores and follower pins 34 may be provided between the bores S5 and S6, and the bores S9 and Si, in the illustrative embodiment.

it is an advantage of the invention that a lock having a high degree of security is provided which is yet eminently simple and compact. However, the principles of the invention are not limited to the illustrative embodiment, but find application in other lock structures, which may have additional features. For example, the

principles of the present invention may be employed in combination with the novel structure disclosed in my above-identified US. Pat. No. 3,541,819, to provide still greater security.

While a preferred embodiment of the invention has been illustrated and described, and reference has been made to various changes and modifications which may be made in the embodiment, it will be apparent that further changes and modifications may be made therein within the spirit and scope of the invention. it is intended that all such changes and modifications be included within the scope of the appended claims.

Having thus described the invention what l claim as new and desire to secure by letters patent is:

ll. in an axial split-pin tumbler-type lock having a lock cylinder and a barrel assembly secured with in the cylinder, said barrel assembly including respective rotatable and stationary parts adjoining each other at an interfacial plane, longitudinal bores in said rotatable and stationary parts, sand bores in respective parts being movable into and out of alignment upon rotation of said rotatable part, tumblers having elements carried by said bores, respective tumblers being reciprocatable longitudinally in aligned bores from a position wherein said intert'acial plane is bridged by a tumbler element to secure the rotatable and stationary parts against relative rotation, to a position wherein said interfacial plane coincides with a tumbler joint to free the parts for relative rotation, and spring means yieldingly urging said tumblers into said position securing said parts, the improved combination with an inwardly extending annular flange on an end of said cylinder and defining a central circular opening into the cylinder and slot means extending radially outwardly from the opening,

said bores in said barrel assembly parts being disposed radially outwardly of said flange opening and portions of the aligned bores being aligned with said slot means to provide access to said tumblers through the slot means,

a circular post connected to said rotatable part for conjoint rotation and having an outside diameter approximating the diameter of said flange opening and extending into the opening to restrict access to the interior of the cylinder through the opening,

means defining a transverse keyway in said post and registrable with said slot means, whereby a key may be inserted into said keyway and slot means for moving said tumblers into said position freeing said parts and for then turning said rotatable part,

an additional longitudinal bore in said stationary part and disposed radially outwardly of said flange opening and out of alignment with said slot means, said additional bore being aligned with one of said bores in said rotatable part in an intermediate position of the rotatable part between operational positions thereof,

an additional tumbler element carried in said additional bore and forming a complete tumbler with an element of one of said first-named tumblers carried in said aligned one bore in said rotatable part,

said complete tumbler being reciprocatable belid additional spring means yieldingly urging said complete tumbler into said position thereof securing said parts,

whereby said rotatable part may be turned by a key inserted as aforesaid, beyond said intermediate position to complete the turning movement thereof, but the rotatable part is secured by said complete tumbler against further turning movement upon reaching said intermediate position in the absence of the key.

2, A lock as defined in claim 1 wherein said tumblers abut on said flange when in said position securing said parts.

3. A lock as defined in claim Tl wherein said keyway is an asymmetrical groove.

4. in combination with a lock as defined in claim l, a key having a shank received in said keyway, and a tang on said shank and insertable through said slot means and internally of the cylinder beyond said flange, said tang having a bitting means thereon and engaging said tumblers for moving them into said positions freeing said parts for relative rotation, said tang turning behind and being retained in the look by said flange as the key is turned.

5. A lock as defined in claim 1 wherein said slot means provides a pair of diametrically opposed slots portions of two sets of aligned bores are in alignment with each slot, and a tumbler is present in each of said sets of bores.

s. in combination with a lock as defined in claim 5, a key having a shank received in said keyway, and a tang on each of opposite sides of said shank and insertable through one of said slots and internally of the cylinder beyond said flange, each said tang having two bittings thereon and engaging respective tumblers for moving them into said positions freeing said parts for relative rotation, said tangs turning behind and being retained in the lock by said flange as the key is turned.

'7. A lock as defined in claim 1 wherein said slot means provides at least two angularly spaced apart slots registrable alternately with said keyway, and said aligned bore portions are in alignment with a first one of the slots, and including further longitudinal bores in said stationary part and disposed radially outwardly of said flange opening and having portions in alignment with a second one of said slots, said further bores being aligned with certain of said bores in said rotatable part and portions of the resulting aligned bores being aligned with said second slot upon effective completion of the turning movement of the rotatable part,

further tumbler elements carried by said further bores and forming complete tumblers with elements of said first-named tumblers carried in said latter aligned bores in said rotatable part, the latter complete tumblers being accessible through said second slot and reciprocatable between positions respectively securing and freeing for relative rotation said parts as in the case of the first-named tumblers, and

further spring means yieldingly urging the latter complete tumblers into said positions thereof securing said parts,

whereby a key may be inserted into and removed from said keyway and one of said slots in each of two angular positions of said rotatable part, for

turning the same from either position to the other upon insertion and for securing the same against rotation and safeguarding the lock code upon removal in each position. 8.. in combination with a lock as defined in claim 7, a key having a shank received in said keyway, and a tang on said shank and insertable alternately through.

each of said slots and internally of the cylinder beyond said flange, said tang having hitting means thereon and engaging said tumblers for moving them into said positions freeing said parts for relative rotation, said tang turning behind said flange and being retained in the lock and in said tumbler engagement by said flange as the key is turned.

9. in an axial split-pin tumbler'type lock having a lock cylinder and a barrel assembly secured within the cylinder, said barrel assembly including respective rotatable and stationary parts adjoining each other at an interfacial plane, the improved combination with an inwardly extending annular flange on an end of said cylinder and defining a central circular opening into the cylinder and at least two slots extending radially outwardly from the opening in angularly spaced relation,

a circular post connected to said rotatable part for conjoint rotation and having an outside diameter approximating the diameter of said flange opening and extending into said flange opening to restrict access to the interior of the cylinder through the opening,

means defining a transverse keyway in said post and registrable alternately with said slots,

first and second pairs of longitudinal bores in said sta tionary part and disposed radially outwardly of said flange opening, said bores each having a portion in alignment with one of said slots and the pairs of bores being aligned with respective slots,

a pair of longitudinal bores in said rotatable part movable into and out of alignment alternately with each pair of bores in said stationary part upon rotation of the rotatable part and portions of the resulting aligned bores being aligned with respective slots,

a tumbler element carried in each of said bores and the elements carried in said rotatable part bores forming complete tumblers respectively with the elements carried in each pair of said stationary part bores upon alignment of respective rotatable and stationary part bores, said complete tumblers being accessible through respective slots and each complete tumbler being reciprocatable longitudinally in the aligned bores from a position wherein said interfacial plane is bridged by a tumbler element to secure the rotatable and stationary parts against relative rotation, to a position wherein said interfacial plane coincides with a tumbler joint to free the parts for relative rotation, and

spring means yieldingly urging said complete tumblers into said positions thereof securing said parts,

whereby a key may be inserted into and removed from said keyway and one of said slots in each of two angular positions of said rotatable part, in each angular position for moving said complete tumblers into said position freeing said parts upon insertion and for then turning said rotatable part into the other position, and for securing the same against rotation and safeguarding the lock code upon removal in each angular position.

in, A lock as defined in claim 9 wherein said flange defines two pairs of diametrically opposed slots extending radially outwardly from said opening in angularly spaced relation, said keyway being registrable alternately with each pair of slots, and including additional longitudinal bores in said stationary part and disposed radially outwardly of said flange opening and including bores having portions in alignment respectively with the slots additional to the first-named slots,

a further pair of longitudinal bores in said rotatable part movable into and out of alignment alternately with the respective additional stationary part bores upon rotation of the rotatable part and portions of the resulting aligned bores being aligned with respective additional slots,

a tumbler element carried in each of said additional bores and in each of said further pair of bores and the elements carried in the latter bores forming complete tumblers respectively with the elements carried in said additional bores upon alignment of the respective bores, said latter complete tumblers being accessible through respective additional slots and each of the latter complete tumblers being reciprocatable between positions respectively securing and freeing for relative rotation said parts as in the case of the first-named tumblers, and

additional spring means yieldingly urging the latter complete tumblers into said positions thereof securing said parts,

whereby said key may be inserted into and removed from said keyway and one of said pairs of slots in each of two angular positions of said rotatable part, in each angular position for moving each of said complete tumblers into said position freeing said parts upon insertion and for then turning said rotatable part into the other position, and for additionally securing the same against rotation and safeguarding the lock code upon removal in each angular position.

iii, A lock as defined in claim it) and including another longitudlnal bore in said stationary part and disposed radially outwardly of said flange opening and out of alignment with said slots, said other bore being aligned with one of said bores in said rotatable part in an intermediate position of the rotatable part between operational positions thereof,

another tumbler element carried in said other bore and forming a complete tumbler with an element carried in said aligned one bore in said rotatable part, the latter complete tumbler being reciprocatable between positions respectively securing and freeing for relative rotation said parts as in the case of the first-named tumblers, and

additional spring means yieldingly urging the lastnamed complete tumbler into said position thereof securing said parts,

whereby said rotatable part may be turned by a key inserted as aforesaid, beyond said intermediate position to complete the turning movement thereof, but the rotatable part is secured by the last-named complete tumbler against further turning movement upon reaching said intermediate position in the absence of the key.

nally of the cylinder beyond said flange, each said tang having two bittings thereon and engaging respective tumblers for moving them into said positions freeing said parts for relative rotation, said tangs turning behind and being retained in the lock by said flange as the key is turned. 

1. In an axial split-pin tumbler-type lock having a lock cylinder and a barrel assembly secured with in the cylinder, said barrel assembly including respective rotatable and stationary parts adjoining each other at an interfacial plane, longitudinal bores in said rotatable and stationary parts, sand bores in respective parts being movable into and out of alignment upon rotation of said rotatable part, tumblers having elements carried by said bores, respective tumblers being reciprocatable longitudinally in aligned bores from a position wherein said interfacial plane is bridged by a tumbler element to secure the rotatable and stationary parts against relative rotation, to a position wherein said interfacial plane coincides with a tumbler joint to free the parts for relative rotation, and spring means yieldingly urging said tumblers into said position securing said parts, the improved combination with an inwardly extending annular flange on an end of said cylinder and defining a central circular opening into the cylinder and slot means extending radially outwardly from the opening, said bores in said barrel assembly parts being disposed radially outwardly of said flange opening and portions of the aligned bores being aligned with said slot means to provide access to said tumblers through the slot means, a circular post connected to said rotatable part for conjoint rotation and having an outside diameter approximating the diameter of said flange opening and extending into the opening to restrict access to the interior of the cylinder through the opening, means defining a transverse keyway in said post and registrable with said slot means, whereby a key may be inserted into said keyway and slot means for moving said tumblers into said position freeing said parts and for then turning said rotatable part, an additional longitudinal bore in said stationary part and disposed radially outwardly of said flange opening and out of alignment with said slot means, said additional bore being aligned with one of said bores in said rotatable part in an intermediate position of the rotatable part between operational positions thereof, an additional tumbler element carried in said additional bore and forming a complete tumbler with an element of one of said first-named tumblers carried in said aligned one bore in said rotatable part, said complete tumbler being reciprocatable between positions respectively securing and freeing for relative rotation the rotatable and stationary parts as in the case of the first-named tumblers, additional spring means yieldingly urging said complete tumbler into said position thereof securing said parts, whereby said rotatable part may be turned by a key inserted as aforesaid, beyond said intermediate position to complete the turning movement thereof, but the rotatable part is secured by said complete tumbler against further turning movement upon reaching said intermediate position in the absence of the key.
 2. A lock as defined in claim 1 wherein said tumblers abut on said flange when in said position securing said parts.
 3. A lock as defined in claim 1 wherein said keyway is an asymmetrical groove.
 4. In combination with a lock as defined in claim 1, a key having a shank received in said keyway, and a tang on said shank and insertable through said slot means and internally of the cylinder beyond said flange, said tang having a bitting means thereon and engaging said tumblers for moving them into said positions freeing said parts for relative rotation, said tang turning behind and being retained in the lock by said flange as the key is turned.
 5. A lock as defined in claim 1 wherein said slot means provides a pair of diametrically opposed slots portions of two sets of aligned bores are in alignment with each slot, and a tumbler is present in each of saiD sets of bores.
 6. In combination with a lock as defined in claim 5, a key having a shank received in said keyway, and a tang on each of opposite sides of said shank and insertable through one of said slots and internally of the cylinder beyond said flange, each said tang having two bittings thereon and engaging respective tumblers for moving them into said positions freeing said parts for relative rotation, said tangs turning behind and being retained in the lock by said flange as the key is turned.
 7. A lock as defined in claim 1 wherein said slot means provides at least two angularly spaced apart slots registrable alternately with said keyway, and said aligned bore portions are in alignment with a first one of the slots, and including further longitudinal bores in said stationary part and disposed radially outwardly of said flange opening and having portions in alignment with a second one of said slots, said further bores being aligned with certain of said bores in said rotatable part and portions of the resulting aligned bores being aligned with said second slot upon effective completion of the turning movement of the rotatable part, further tumbler elements carried by said further bores and forming complete tumblers with elements of said first-named tumblers carried in said latter aligned bores in said rotatable part, the latter complete tumblers being accessible through said second slot and reciprocatable between positions respectively securing and freeing for relative rotation said parts as in the case of the first-named tumblers, and further spring means yieldingly urging the latter complete tumblers into said positions thereof securing said parts, whereby a key may be inserted into and removed from said keyway and one of said slots in each of two angular positions of said rotatable part, for turning the same from either position to the other upon insertion and for securing the same against rotation and safeguarding the lock code upon removal in each position.
 8. In combination with a lock as defined in claim 7, a key having a shank received in said keyway, and a tang on said shank and insertable alternately through each of said slots and internally of the cylinder beyond said flange, said tang having bitting means thereon and engaging said tumblers for moving them into said positions freeing said parts for relative rotation, said tang turning behind said flange and being retained in the lock and in said tumbler engagement by said flange as the key is turned.
 9. In an axial split-pin tumbler-type lock having a lock cylinder and a barrel assembly secured within the cylinder, said barrel assembly including respective rotatable and stationary parts adjoining each other at an interfacial plane, the improved combination with an inwardly extending annular flange on an end of said cylinder and defining a central circular opening into the cylinder and at least two slots extending radially outwardly from the opening in angularly spaced relation, a circular post connected to said rotatable part for conjoint rotation and having an outside diameter approximating the diameter of said flange opening and extending into said flange opening to restrict access to the interior of the cylinder through the opening, means defining a transverse keyway in said post and registrable alternately with said slots, first and second pairs of longitudinal bores in said stationary part and disposed radially outwardly of said flange opening, said bores each having a portion in alignment with one of said slots and the pairs of bores being aligned with respective slots, a pair of longitudinal bores in said rotatable part movable into and out of alignment alternately with each pair of bores in said stationary part upon rotation of the rotatable part and portions of the resulting aligned bores being aligned with respective slots, a tumbler element carried in each of said bores and the elements carried in said rotatable part bores forming compLete tumblers respectively with the elements carried in each pair of said stationary part bores upon alignment of respective rotatable and stationary part bores, said complete tumblers being accessible through respective slots and each complete tumbler being reciprocatable longitudinally in the aligned bores from a position wherein said interfacial plane is bridged by a tumbler element to secure the rotatable and stationary parts against relative rotation, to a position wherein said interfacial plane coincides with a tumbler joint to free the parts for relative rotation, and spring means yieldingly urging said complete tumblers into said positions thereof securing said parts, whereby a key may be inserted into and removed from said keyway and one of said slots in each of two angular positions of said rotatable part, in each angular position for moving said complete tumblers into said position freeing said parts upon insertion and for then turning said rotatable part into the other position, and for securing the same against rotation and safeguarding the lock code upon removal in each angular position.
 10. A lock as defined in claim 9 wherein said flange defines two pairs of diametrically opposed slots extending radially outwardly from said opening in angularly spaced relation, said keyway being registrable alternately with each pair of slots, and including additional longitudinal bores in said stationary part and disposed radially outwardly of said flange opening and including bores having portions in alignment respectively with the slots additional to the first-named slots, a further pair of longitudinal bores in said rotatable part movable into and out of alignment alternately with the respective additional stationary part bores upon rotation of the rotatable part and portions of the resulting aligned bores being aligned with respective additional slots, a tumbler element carried in each of said additional bores and in each of said further pair of bores and the elements carried in the latter bores forming complete tumblers respectively with the elements carried in said additional bores upon alignment of the respective bores, said latter complete tumblers being accessible through respective additional slots and each of the latter complete tumblers being reciprocatable between positions respectively securing and freeing for relative rotation said parts as in the case of the first-named tumblers, and additional spring means yieldingly urging the latter complete tumblers into said positions thereof securing said parts, whereby said key may be inserted into and removed from said keyway and one of said pairs of slots in each of two angular positions of said rotatable part, in each angular position for moving each of said complete tumblers into said position freeing said parts upon insertion and for then turning said rotatable part into the other position, and for additionally securing the same against rotation and safeguarding the lock code upon removal in each angular position.
 11. A lock as defined in claim 10 and including another longitudinal bore in said stationary part and disposed radially outwardly of said flange opening and out of alignment with said slots, said other bore being aligned with one of said bores in said rotatable part in an intermediate position of the rotatable part between operational positions thereof, another tumbler element carried in said other bore and forming a complete tumbler with an element carried in said aligned one bore in said rotatable part, the latter complete tumbler being reciprocatable between positions respectively securing and freeing for relative rotation said parts as in the case of the first-named tumblers, and additional spring means yieldingly urging the last-named complete tumbler into said position thereof securing said parts, whereby said rotatable part may be turned by a key inserted as aforesaid, beyond said intermediate position to complete the turning movement thereof, but tHe rotatable part is secured by the last-named complete tumbler against further turning movement upon reaching said intermediate position in the absence of the key.
 12. A lock as defined in claim 11 wherein said tumblers abut on said flange when in said positions securing said parts.
 13. In combination with a lock as defined in claim 11, a key having a shank received in said keyway, and a tang on each of opposite sides of said shank and insertable through one of said slots in each pair and internally of the cylinder beyond said flange, each said tang having two bittings thereon and engaging respective tumblers for moving them into said positions freeing said parts for relative rotation, said tangs turning behind and being retained in the lock by said flange as the key is turned. 